It is well known that epoxy resin, one of the thermoset resins, is a high-molecular-weight material having good heat resistance, mechanical properties, electric insulating properties, adhesiveness and weather resistance; and epoxy resin is used as paint, an electric insulating material, a stabilizer for vinyl chloride, a coating and a matrix resin of fiber-reinforced complex material. It may fairly be said that these widely varying industrial applications of epoxy resin have resulted from the development of curing technology; and, thus, the effect of the curing agent on epoxy resin is enormous.
Specifically, epoxy resin requires the use of a curing agent in order to create a three-dimensional net structure; and, therefore, the heat resistance and the final mechanical properties of the epoxy resin may be different depending on the nature of this curing agent. Curing agents having components harmful to the human body (e.g., amine compounds) are frequently used, which results in many problems. The use of such curing agents in combination with additives such as accelerators, plasticizers, fillers, mold-releasing agents, flame retardants, diluents and dyes largely reduces the physical properties of the epoxy resin.
Further, the use of a curing agent comprising an amine (e.g., DDS: 4,4-diaminodiphenylsulfone) may result in decreased processability due to its high viscosity; and, thus, the production of molded products using such a curing agent becomes very difficult.
On the other hand, in the electric and electronic industries and the automobile industries, which lead the leading-edge industries, one would expect to see the development of epoxy resins that are capable of curing at a relatively low temperature of approximately 80 to approximately 120.degree. C. in a short time, are capable of generally completely curing within approximately 30 to approximately 120 minutes, are capable of being stored at room temperature more than about six months, are capable of maintaining their physical properties at high temperatures more than approximately 180.degree. C., and are cost-effective compared to other high-heat-resistant resins such as bismaleimide triazine resins or polyimide resins. However, there appears to be no report of such resins being developed.